Adjustable trigger stop



Aug 19, 1947. J. J. sTALLER I 2,425,761

I V ADJUSTABLE'TRIGGER STOPv Filed Jan. 7, 1946 o Ik m 4, Y Y h V AA/////////////////\ /\//Vw@A M v. .b om

Junk J. El =halle-r @yi/.Mw fm Patented Aug. 19, 1947 UNET 6 Claims.

(Granted under the act of amended AprilV 30,

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

'Ihis invention relates to a machine gun and particularly toa novel and improved stop for the trigger bar generally provided in such guns.

In the U. S. Army models of the Browning machine guns, for example, the caliber 50, M2, machine gun, a trigger bar member is provided comfprising a relatively long member pivotally mounted at its central portion to the receiver and constructed to provide an operative connection between the scar on the bolt of such machine gun and a back plate trigger. Elevating the rear end of such trigger bar has the eiect of depressing the forward end toward the bolt in position to trip o'? the scar as the bolt approaches its battery position.

Considerable difficulty has heretofore been experienced in correctly positioning such trigger bar with respect to the bolt and the scar. A xed stud is generally provided, depending from the top plate of the machine gun, and such stud is arranged to limit the upward movement or the rear end of the trigger bar. When all of the cooperating components are produced to exact dimensions, then the xed trigger bar stop should limit the movement of the rear end of the trigger bar so that the iront end clears the top of the bolt by a few thousandths of an inch. In quantity production of machine gun components, however, it is not possible to produce dimensioi ally identical components. Accordingly, even under the best manufacturing conditions, an accumulation of tolerances in the cooperating members quite often produces assemblies with one of two extreme conditions existing. For example, the trigger bar stop may be too short relative to the various cooperating elements so that the front end of the trigger bar actually interferes with and rides upon the top surface of the bolt. This condition, while undesirable from the standpoint of wear of the components, is dan-1 gerous in that it has the effect of tripping the scar slightly earlier than usual and hence there is a possibility of ring the cartridge before the action is safely locked. Or in the other extreme combination of tolerances, the trigger bar stop is relatively long compared to the other components and the forward end of the trigger bar is stopped a substantial distance above the top of the bolt. If this separation is extrem-e, it is possible for the trigger bar to miss the scar entirely and hence be inoperative to lire the gun.

Accordingly, it is an object of this invention to provide an improved trigger bar stop for a machine gun. A particular object of this invention is to interchangeably provide an adjustable trigger bar stop for a Browning machine gun,

March 3, 1883, as

as the U. S. machine gun,

such, for example, caliber .50, M2.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is a side elevational view, partly in section, of a machine gun incorporating a trigger bar stop in accordance with this invention,

Iliig. 2 is an isometric view of the assembly of components constituting one modication of a trigger bar stop in accordance with this invention.

Fig. 3 comprises top and front elevational views of an assembly of components constituting a sccond modification of this invention.

Fig. 4 comprises a side and a partial angular elevational View of the spring utilized in the construction of Fig. 3.

In any modification of a military weapon to incorporate improvements, the primary criterio-n is that such modification be completely interchangeable With existing Weapons and be capable of being applied to the gun in the eld. In accordance with this invention, an adjustable trigger bar stop is provid-ed for Browning-type U. S. Army machine guns which is interchangeable with existing guns and may be applied Without the use of special tools and equipment.

In Fig. 1 there is shown a machine gun receiver l having side plates 2 and 3 and top plate 4. A bolt 5 is arranged in conventional fashion to reciprocate within receiver l and on the upper surface of bolt 5, a conventional scar 6 is provided to trip the ring mechanism (not shown). An integral lug i is provided in depending relationship on top plate 4 and a trigger oar 8 is pivotally mounted within receiver l by means of a pin 9 passing through suitable holes intrigger bar S and lug l. A conventional trigger bar stop lll may be provided comprising a depending stud-like member mounted in top plate l immediately overlying the rear end ll of trigger bar 8. It should be understood, however, that it is immaterial to the practice of this invention whether or not the standard xed trigger bar stop l t remains in the weapon.

The adjustable trigger stop unit comprises a rectangular base member 20 (Fig. 2) on which is pro-vided a hollow stud Bil which in turn is externally threaded to receive an adjustable nut do. Base member 29 is secured in depending relationship to top plate i by means of a special screw 2l which is substituted for the standard rear top plate cover screw. The hollow stud 38 may be formed integrally with base member 253 as shown or may be secured in a suitable hole in the base member 2t. In any event, a cylindrical opening 22 is provided extending through both base member 20 and stud member 30 which is large enough to receive the standard fixed trigger bar stop therein. The end of such standard trigger bar stop, if retained in the gun, is, however, shortened by cutting or filing oir approximately one-tenth of an inch. Adjusting nut 40 is screwed on to the external threads provided on stud 3i). Adjusting nut 40 is constructed to lie in the path of trigger bar 8 and serves as a stop therefor and rotation of nut M3 on stud 3i] serves to adjust the vertical position of the nut with respect to the trigger bar stop.

In the modification disclosed in Figs. 1 and 2, rotation of the adjusting nut G after it has been set to proper position is prevented by the interengagement of the trigger bar 8 between depending integral prongs il provided on adjusting nut 4D.

In the modification illustrated in Figs. 1 and 2, three such prongs are provided and hence adjustments can be made at intervals of 1/3 of a turn of adjusting nut'l, but obviously any number of prongs may be utilized as desired.

A further modification of this invention is disclosed in Figs. 3 and 4. As illustrated in these gures, a U shaped, leaf-type latching spring 55 is provided having one arm 5l somewhat longer than the other arm 52. A hole 53 is provided in arm 5l of suitable dimensions to accommodate hollow stud 3D. An arcuate recess 555 is provided in arm 52 in alignment with hole 53. An adjusting nut Sii is provided which is screwed onto hollow stud 36 after latching spring 55 is assembled thereon.

There is provided a base to member 2t but having a cut-out portion 23. Arm 5! of latching spring 55.3 is bent to form a projecting portion 55 which in assembly ts snugly in cut-out portion 23 and thereby secures spring 5B against rotation.

An integral detent 55 is formed in arm 52 of spring 5e in such manner as to engage in serrations 5l provided on the top surface of adjusting nut til.

'Ihe latching spring 55 thus serves to resiliently secure nut 55 against rotation. Nut 6d can thus be readily adjusted to and maintained in a proper position to function as a stop for trigger bar 8.

It will be apparent that the modification shown in Fig. 3 has the further advantage of permitting adjustment of the trigger bar stop merely by removal of the back plate (not shown) of the gun. It is not necessary to disassemble the trigger bar as is the case with the construction of Fig. 2.

I claim;

1. For use in a machine gun having a movable trigger bar, a trigger bar stop comprising a threaded stud arranged to be secured to the gun and disposed in the path of the trigger bar, a nut member mounted on said stud and arranged to be engaged by the trigger bar to limit the movement thereof, and a plurality of axially extending projections provided about the periphery of said nut member, said projections being spaced apart relative to each other so as to receive the trigger bar therebetween in any one of a plurality of rotative positions of said nut member of said stud.

2. For use in a machine gun having a movable trigger bar, a trigger bar stop comprising a threaded stud arranged to be secured to the gun and disposed in the path of the trigger bar, a nut member mounted on said stud and arranged to member 2Q similar be engaged by the trigger bar to limit the movement thereof, a leaf spring mounted in surrounding relation on said stud between said nut member and the machine gun, means for non-rotatively securing one end of said leaf spring to the machine gun, and a detent formed on said leaf spring, said nut member having a plurality of circumferentially spaced notches therein arranged to selectively receive said detent.

3. For use in a machine gun having a trigger bar pivotally movable in a vertical plane, a trigger bar stop comprising a plate-like base member arranged to be secured to the machine gun in a position overlying the trigger bar, a threaded stud formed on said base member and projecting into the path of the trigger bar, a nut member'mounted on said stud and adapted to be engaged by the trigger bar to limit the movement thereof, a generally U-shaped latch spring having both arms mounted on said stud between said nut member and said base member, said base member having a recess constructed and arranged to receiVe one arm of said latch spring therein to nonrotatively secure said latch spring to said base member, and a detent formed on the other arm of said latch spring, said nut member having a plurality of circumferentially spaced notches arranged to selectively receive said detent therein, thereby resiliently securing said nut member in any selected one of a plurality of rotative positions on said stud.

fi. In a machine gun having a trigger bar pivotally movable in a vertical plane, a iixed stud-like trigger bar stop cooperating with said trigger bar to limit the movement thereof, the improvement comprising, a hollow threaded stud member arranged to surround the xed trigger bar stop, means for securing said stud member to the machine gun in surrounding relation to the fixed trigger bar stop, a nut member mounted on said stud member and arranged to be engaged by the trigger bar to limit the movement thereof, and means for securing said nut member in any selected rotative position on said stud member.

5. The combination defined in claim 4l wherein said last mentioned means comprises a plurality of axially extending projections provided about the periphery of said nut member, said projections being spaced apart relative to each other so as to receive the trigger bar therebetween in any selected one of a plurality of rotative positions of said nut member on said stud member.

6. The combination deined in claim l wherein said last mentioned means comprises a leai spring mounted in surrounding relation on said stud member between said nut member and the machine gun, means for non-rotatively securing one end of said leaf spring to the machine gun, and a detent formed on said leaf spring, said nut member having a plurality of circumferentially spaced notches arranged to selectively receive said detent therein.

JACK J. STALLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

